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Assistance please

4

4dude

Some friends of mine @ a local radio station are having some problems...

They have anisocoupler protecting thier STL antenna which is on the same tower as the main stick...(Usually 50k)

The problem is,the hi RF keeps frying the isocoupler and they have to back down to 5k until they get it fixed........

Are there any CHEAP ways of protecting the isocoupler that he as an engineer can do?? It has to be where it is to make a 95%+ signal to the recieving station (About 20 miles away) It cant be taken off that tower or the signal isnt good enough to be heard properly on the recieving end......

I suggested adding a SATELLITE DISH between the isocoupler and the main stick,that might shield it enough to stop the damage.....

They have gone thru about 2 or 3 of them now.......

Any Ideas??
 
I'll take a stab at it.

It sounds like a VSWR (reflective power) issue with regard to the main antenna. Perhaps there's a problem with the main antenna, or maybe the STL antenna needs to be relocated at a different spot on the tower.

My $0.02, FWIW.

R
 
Well i suppose with some field testing it might be able to be re-located on the tower but im not sure on that.. But i think your right,re-locating it MIGHT take it out of the direct stream of RF and still have a useable signal @ the recieving end....
 
The Dude said:
Well i suppose with some field testing it might be able to be re-located on the tower but im not sure on that.. But i think your right,re-locating it MIGHT take it out of the direct stream of RF and still have a useable signal @ the recieving end....
Click to expand...

If I were in this situation, I'd first have the main broadcast antenna checked and also the coax line leading up to the antenna (the main one, not the STL antenna). I am assuming this is an FM station.

R
 
In several situations such as this one where the base voltage was very high and
the isocouplers kept blowing I used two Scala miniflectors facing each other very
closely spaced at the tower base .....PROBLEM SOLVED...every time

Chris Hall
 
chrish said:
In several situations such as this one where the base voltage was very high and
the isocouplers kept blowing I used two Scala miniflectors facing each other very
closely spaced at the tower base .....PROBLEM SOLVED...every time

Chris Hall
Click to expand...
You took the words right out of my mouth...Problem solved permanently and at a cost that's not much greater than yet another isocoupler.
 
chrish said:
In several situations such as this one where the base voltage was very high and
the isocouplers kept blowing I used two Scala miniflectors facing each other very
closely spaced at the tower base .....PROBLEM SOLVED...every time
Click to expand...
Sounds interesting chris,ill have to let him know this!

Thanx for your input!
 
if you need more info I can send you some pictures of a recent installation by
a friend Grady Moates when he diplexed on to a high power 5 tower array I have
taken care of for years. During recent rework of the night pattern for a power increase we also added a dish on the #1 tower for our own future use and will
use the same arrangement at the base when the time comes.
I have also used it on Nantucket over salt water path of 25 miles when I had some minor ownership in the station, even with the weak STL signal it worked like a charm. Also used it in Florida in the 70's

hope this helps,.
Chris Hall
 
To clairify. This is the STL transmit end of the path and not the receive end?

If so, the back to back Scala's won't work legally. Doubt the FCC would license a 1-foot path to a passive repeater.
 
Yes its the transmit end that keeps blowing.. Its next to 50k of RF....

Yes chris i would love seeing those pictures :)
 
The path loss will take at least a 6db or greater hit with this configuration according to George Marti. You might want to consider this in your calculations if path loss is critical. Other alternatives are possible though. What is height of tower in electrical degrees? A stub attachment may be possible if the tower is greater than 90 degrees in electrical length. At 50kw, nothing is "cheap", just more (or less) expensive in all cases.
Good luck!
w/
 
Get Kintronic Labs to make you an isocoupler that won't burn up. It won't be cheap initially, but will be worth it in the long run.
 
I hear the company doesnt seem to care and as a result they are trying to do it on thier own. (Which isnt easy w/o $$$ from the main company)
 
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